The Carolina Panthers' legacy is built upon the shoulders of great defenses and defensive greats, from the days of Sam Mills and Kevin Greene to the John Fox era of Julius Peppers and Jon Beason.

Panthers head coach, Ron Rivera, also knows a thing or two about great defenses.

As a player, Rivera was a reserve linebacker on the legendary 1985 Chicago Bears defense.

As a defensive coordinator for the San Diego Chargers, he coached one of the most feared defenses of the past decade.

Now the team Rivera coaches, the Carolina Panthers, is coming off one of its greatest offensive seasons, but the defense was among the NFL's worst in 2011.

Carolina's offense, led by offensive mastermind Rob Chudzinski, has an enviable blend of youth, talent and experience, but it is up to defensive coordinator Sean McDermott and the eleven guys lining up across from the likes of Drew Brees and Michael Turner to determine the Panthers' fate.

How the Panthers' defense fares in 2012 will determine whether Carolina improves upon last season's 6-10 record and makes a push for the playoffs this season, or whether the team watches from the bleachers like the rest of us.

Here are five reasons to believe the Panthers' defense will "keep pounding" opponents all the way to a playoff berth this season.

Stronger Interior Line

Ron Edwards was the Carolina Panthers' starting defensive tackle for a few hours on the first day of training camp in 2011.

Then he tore his biceps on the first play of his first practice with the Panthers and his season was over.

With Edwards out, Carolina relied on a couple of rookie third-rounders, Sione Fua and Terrell McClain, to play the all-important defensive tackle positions.

Granted, Fua would have likely been a starter anyway, but the lack of veteran leadership on the interior line and the absence of defensive captain and vocal leader, linebacker Jon Beason, who tore his Achilles in the first game of the season, proved too much to overcome.

The rookies were pushed around often and, according to Ron Rivera, they did not always execute their assignments properly, which was partially due to their inexperience and a lack of communication caused by the absence of Edwards and Beason. Via the Charlotte Observer:

We may have been lined up properly, but we didn’t fit the run properly. Probably the best way to put it – in some instances, in some circumstances, we had a lack of communication.

Edwards and Beason will be in the lineup, and Carolina's interior line rotation of Sua, McClain, Andre Neblett and Frank Kearse has a year of experience under its belt.

Though the Panthers may not be a top-ten defense against the run this season, they will improve markedly over 2011, when they allowed 130.8 rushing yards per game, good for 25th best—or eighth worst—in the NFL.

Improved Pass Rush

Nick Laham/Getty ImagesCharles Johnson (95) needs to be a sack master in 2012.

The Carolina Panthers did not put enough pressure on opposing quarterbacks last season, and that lack of pressure contributed mightily to their 24th-ranked pass defense in 2011.

Starting defensive ends Charles Johnson and Greg Hardy failed at getting to the quarterback with great frequency, combining for only 13 sacks last year.

That total was eclipsed or matched by seven different players in the NFL, and neither player finished in the top twenty league-wide.

The Panthers drafted the Big 12's defensive player of the year, Oklahoma defensive end Frank Alexander, with the first of their two fourth-round picks, in an effort to improve the pass rush this season.

Johnson and either Hardy or Alexander will bookend Carolina's defensive line this season, and they will be helped by high-motor rotational players Antwan Applewhite and Thomas Keiser, who both showed a proclivity to get to the quarterback in limited action last year.

If this group fails to get to the quarterback this season, it will be another long season for the Panthers' secondary, and Cam Newton & Co. will be forced to win a lot of shootouts in 2012.

Upgraded Pass Coverage

Gregory Shamus/Getty ImagesChris Gamble (20) was the lone bright spot in the Panthers' secondary last season.

Chris Gamble regained his lock-down form and became a shutdown cornerback in 2011.

But if Gamble blanketed receivers, Captain Munnerlyn was the cross between an afghan and a shawl—lightweight and full of holes.

Josh Norman, Brandon Hogan and "Cap" will compete for the second cornerback spot in training camp, and I believe Norman will win the position while Hogan and Munnerlyn will split nickle and dime duties.

Norman, Carolina's rookie fifth-round draft pick, is slightly larger and more athletic than Munnerlyn, and Hogan, who is coming off an ACL tear that kept him sidelined for most of his rookie season a year ago.

He also has the arrogance and positive attitude that we have come to expect from the NFL's best cornerbacks.

Granted, he will likely get burned a fair amount in his first season covering NFL receivers after playing college ball at FCS school Coastal Carolina, but Norman is up for the challenge and will be a significant upgrade over Munnerlyn, who was a liability at the position last year.

Healthy Linebacker Corps

Streeter Lecka/Getty ImagesThe Panthers get their defensive captain back with a healthy Jon Beason.

I saved this slide for last because, when healthy, the Carolina Panthers' linebackers corps is among the top-five in the NFL.

The Panthers' linebackers were decimated by injuries in 2011 and played with a handful of starting combinations before settling on James Anderson, Dan Connor and Jordan Senn late in the season.

Carolina should be healthy at linebacker this season, though, with the addition of first-round draft pick, Luke Kuechly, and Jon Beason is expected to be back at full strength after tearing his Achilles in the first game.

Thomas Davis is also on pace to return to action after his third ACL surgery, though time will tell whether or not he will return at full-strength.

Barring injury at training camp and throughout the season, the Panthers will have improved linebacker play in 2012, and that will help Carolina defend better against the pass and the run.